I am asking for advice on the best (safest) way to support the weight of the 4.0L HO engine in my '99 XJ in order to replace the motor mount.

According to the FSM, it simply states to "support the engine", which in and of itself is not terribly helpful.

I checked the Hanes manual I have, and it states to use a floor jack and a piece of wood, to spread out the force, and to lift the engine via the oil pan enough to take tension off of the engine to unbolt the mount and replace it.

That sounds like the detail I need, but honestly I do not feel real comfortable supporting part of the engine on the oil pan. Can the oil pan really take that kind of stress without cracking?

My question is, has anyone else supported the engine this way or found another, safer, location to use a floor or bottle jack?

The oil pan can definently take it, I've got big *** dents in mine from bigger rocks with more force than the weight of the engine. And I've say down plenty of 4.0L's on the oil pan before. I would say the BEST would be to use a cherry picker and hook it onto the head bolts. But if that's not possible, use a jack and a piece of wood. To keep it balanced you could bolt the piece of wood to the frame and put jackstands under it.

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"Nitrous? So is that like viagra for your Jeep?" -mom

Block and jack under the oil pan works great. Just don't try jacking up the entire vehicle. Loosen your motor mount bolts first and jack then loosen then jack and loosen until your motor is high enough to remove the mounts. The fan shroud is going to get in the way also....so I would remove that...